Internet Protocol (IP) based communication sessions used for voice, streaming media, or other multimedia sessions have become pervasive in today's communication networks. The IP networks supporting these sessions have evolved to match both the increasing demand and the increasing expectations for reliability. In essence, consumers are expecting packet-based communications to rival the reliability of traditional circuit-switched communications afforded by the Public Switched Telephone Network (PSTN). Efforts to increase reliability in the IP networks have led to providing massive redundancy of various network nodes that support or facilitate the communication sessions.
In Session Initiation Protocol (SIP) based networks, a SIP proxy server is used to afford a communication terminal access to the SIP network as well as to establish and control communication sessions involving the communication terminal. In an effort to increase reliability of the SIP network, each SIP proxy is replicated one or more times to afford redundancy in case one or more SIP servers fail. Providing such redundancy has proven costly, and often futile.
The most common failures in SIP networks are not related to the SIP proxies, but instead, the underlying network equipment such as the routers, switches, and gateways, where redundancy is not specifically provided. In many instances, an underlying network failure causes an outage in a portion of the SIP network; however, the SIP server and the redundant SIP servers remain functioning. In essence, the SIP proxy and the communication terminal are simply isolated from each other, but are still operational. As such, the affected SIP proxy and communication terminal may be able to communicate with other entities from which they are not isolated. These other entities may include geographically remote SIP proxies and communication terminals for which the network outage is not causing isolation.
Accordingly, there is a need for a technique to provide a reliable network without requiring the normal redundancy provided in today's networks. There is a further need to provide a network that provides reliability in light of failures occurring in the underlying network equipment, which result in localized network outages in certain geographic locations.